Valve Sizing

Bulletin 1-I

C v1 , F L1

Fpv

(p −F )

Cv1= Cv 2

1

Fpv

(p − F )
L 1

2

L2

∆pm ax (1) = F

p1

∆pmax (2) =F

2

1

C v 2 ,F L 2

FL1 > FL 2

pv pvc p2I p2II p2III p2IV HANDBOOK
FOR CONTROL
VALVE SIZING

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HANDBOOK
FOR CONTROL
VALVE SIZING
CONTENTS
NOMENCLATURE
VALVE SIZING AND SELECTION
1

PROCESS DATA

2

VALVE SPECIFICATION

3

FLOW COEFFICIENT
3.1 KV coefficient
3.2 Cv coefficient
3.3 Standard test conditions

4

SIZING EQUATIONS
4.1 Sizing equations for incompressible fluids (turbulent flow)
4.2 Sizing equations for compressible fluids
(turbulent flow)
4.3 Sizing equations for two-phase fluids
4.4 Sizing equations for non turbulent flow

5

PARAMETERS OF SIZING EQUATIONS
5.1 Recovery factor FL
5.2 Coefficient of incipient cavitation xFZ and coefficient of constant cavitation Kc
5.3 Piping geometry factor Fp
5.4 Combined liquid pressure recovery factor and piping geometry factor of a control valve with attached fittings FLP
5.5 Liquid critical pressure ratio factor FF
5.6 Expansion factor Y
5.7 Pressure differential ratio factor xT
5.8 Pressure differential ratio factor for a valve with attached fittings xTP
5.9 Reynolds number factor FR

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Symbols

Description

Units (note)

Cd

Specific flow coefficient = Cv/ d2

various

Cv

Flow coefficient

U.S. gallons/min

d

Nominal valve size

mm

D

Internal diameter of piping

mm

Fd

Valve style modifier

dimensionless

FF

Liquid critical pressure ratio factor

dimensionless

FL

dimensionless

FP

Liquid pressure recovery factor for a control valve without attached fittings Combined liquid pressure recovery factor and piping geometry factor of a control valve with attached fittings
Piping geometry factor

dimensionless

FR

Reynolds number factor

dimensionless

Fγ

Specific heat ratio factor = γ/1.4

dimensionless

KB1